c_cpp 一个加载着色器文件，编译和链接到着色器程序的函数。

Posted 2021-05-14

std::string readShaderSource(const char* shaderfile)
{
	std::ifstream ifile(shaderfile);
	std::string filetext;

	if (!ifile.good())
	{
		std::cerr << "Failed to load file" << std::endl;
	}
	std::stringstream shaderdata;
	shaderdata << ifile.rdbuf();
	ifile.close();
	const std::string &shaderString = shaderdata.str();

	//std::cout << shaderString << std::endl;
	return shaderString;
}

GLuint createShaderProgram(const char* vshader_file, const char* fshader_file)
{
	struct Shader {
		const char* filename;
		GLenum		type;
		const GLchar*		source;
	} shaders[2] = {
		{ vshader_file, GL_VERTEX_SHADER, NULL },
		{ fshader_file, GL_FRAGMENT_SHADER, NULL }
	};


	GLuint program = glCreateProgram();

	// Load shader and check
	for (int i = 0; i < 2; i++)
	{
		Shader& s = shaders[i];
		std::string shader_string = util::readShaderSource(s.filename);
		s.source = shader_string.c_str();
		GLint const shader_length = shader_string.length();
		if (shaders[i].source == NULL){
			std::cerr << "Failed to read " << s.filename << std::endl;
			exit(EXIT_FAILURE);
		}

		//printf("%s\n", s.source);

		GLuint shader = glCreateShader(s.type);
		glShaderSource(shader, 1, &s.source, &shader_length);
		glCompileShader(shader);

		GLint compiled;
		glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
		if (compiled == GL_FALSE)
		{
			std::cerr << "Failed to compile " << s.filename << std::endl;
			GLint logsize;
			glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &logsize);
			char* logmsg = new char[logsize];
			glGetShaderInfoLog(shader, logsize, NULL, logmsg);
			std::cerr << logmsg << std::endl;
			delete[] logmsg;
			exit(EXIT_FAILURE);
		}

		//delete[] s.source;

		glAttachShader(program, shader);
	}

	// Link program and check
	glLinkProgram(program);

	GLint linked;
	glGetProgramiv(program, GL_LINK_STATUS, &linked);
	if (linked == GL_FALSE) 
	{
		std::cerr << "Shader program failed to link" << std::endl;
		GLint  logsize;
		glGetProgramiv(program, GL_INFO_LOG_LENGTH, &logsize);
		char* logmsg = new char[logsize];
		glGetProgramInfoLog(program, logsize, NULL, logmsg);
		std::cerr << logmsg << std::endl;
		delete[] logmsg;

		exit(EXIT_FAILURE);
	}
	glUseProgram(program);
	return program;
}